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The Hybrid III Dummy Family Subject to Loading by a Motorized Shoulder Belt Tensioner 2008-01-0516

Motorized shoulder belt tensioning is a new automotive seatbelt technology which has shown promise to reduce automotive crash injuries. The current study was conducted to determine if the Hybrid III family of dummies is an appropriate biofidelic surrogate for studying motorized shoulder belt tensioning. The objective was to measure torso retraction time, torso position, torso velocity, internal resistive moment, changes in torso curvature and the center of rotation of torso extension during seatbelt tensioning for the Hybrid III family.

A previous study developed a protocol and test fixture to measure the biomechanics of volunteers subject to quasi-static loading by a motorized shoulder belt tensioner. A fixture supported the occupant leaning forward and applied shoulder belt tension. Kinematics were quantified by analyzing the motion of reflective markers on the dummy using an eight camera digital video system. A three axis load cell measured internal resistance to extension. This test method was applied to the 6-year-old, the 5th female and 50th male Hybrid III dummies.

Peak shoulder belt loads of 131-141 N were applied to the dummies causing torso deflections of 8°-13° in 0.42-0.57 seconds. The data was compared to the responses of human volunteers. Peak shoulder belt loads of 82 N-92 N were applied to volunteers causing torso deflections of 42°-58° in 0.78-0.95 seconds. The center of rotation for the Hybrid III torso was further from the H-point than observed in volunteer studies. The out-of-plane belt-side shoulder drop and twist was much less for the dummies than observed for the volunteers. The dummy biofidelity was limited in this environment. They were found to be poor human surrogates for motorized shoulder belt tensioning of out-of-position occupants. The stiff lumbar spine and molded seated pelvis lacked the mobility observed in relaxed volunteers.